270 THE- VOYAGE OF H.M.S. CHALLENGER. 
are six papulze round each tabulum, corresponding in position to the angles of the hexagon, 
and they are separated from one another by the stellate prolongations between the plates. 
The five primary interradial plates (basals) are clearly discernible and are distinctly larger 
than any of the other tabula. They are all equidistant from the centre, being from four 
to five times their own diameter distant. One bounds the adcentral side of the madre- 
poriform body and is larger than the others. The dorso-central plate may also be 
distinguished. 
The supero-marginal plates are fifteen in number, counting from the median interradial 
line to the extremity. They form a conspicuous border to the abactinal area and their 
breadth and length are subequal, except at the extremity, where they gradually diminish 
in size, and the breadth is in excess of the length; the plates are slightly convex and form 
a bevelled edge to the paxillar area. Their surface is covered with small, low, truncate, 
crowded granules, excepting a small irregular oval naked space on the abactinal surface. 
A number of the plates bear one of the small excavate pedicellarie, similar to those 
already described above, and these are frequently situated in the naked oval space. 
The infero-marginal plates correspond to the superior series, and are similarly covered 
with small, low, crowded granules. Only five or six plates on each side of the median 
interradial line have small naked areas on the actinal side, which are very much less 
than those on the superior series and gradually diminish as they proceed along the ray. 
It would appear that pedicellarize are normally not present on the infero-marginal plates. 
In the example under notice I have only found one plate thus furnished. 
The adambulacral plates are a little broader than long, and their armature consists of 
a marginal series of four or sometimes five short equal spinelets, irregularly cylindrical or 
often more or less subprismatic, with roundly truncate tips, frequently subclavate, and on 
the outer half of the ray more or less compressed in the direction of the axis of the ray. 
At a short distance behind these are normally three low, thick, dumpy, subclavate, papil- 
liform spinelets forming a slightly arched line traversing the plate diagonally, the aboral 
end of the series being nearest the marginal or furrow spinelets. External to these are a 
few (about five to seven) low, truncate, prismatic granules, which may either form two 
subregular parallel lines, or a diagonal line subparallel with the second series of dumpy 
papillz, with one or more granules filling in the vacant spaces at the corners left by the 
obliquity of the line. These outer granules are scarcely distinguishable from those on the 
adjacent actinal intermediate (ventral) plates to be described below. In two or three rare 
instances an incipient pedicellaria is present on the adambulacral plates, but not more than 
that number occur in the whole of the adambulacral plates of the example under description. 
Pedicellaria may therefore be said to be not present normally. Near the extremity of 
the ray there are not more than three furrow spinelets on each plate, and finally only two. 
And the second row of dumpy papilliform spinelets is at the same time represented by only 
two, one of which is much larger than the other, and on the terminal seventeen or eighteen 
